This is the Competing Continuation application of the National Alzheimer's Coordinating Center (NACC). Between about 1984 and 1997, no data were centrally collected for the 29 Alzheimer's Disease Centers (ADCs) funded by the National Institute on Aging. Establishment of an interim data center and a Minimum Data Set in about 1997 led to the NIA issuance of an RFA for an Alzheimer's Disease Data Coordinating Center. Since receiving the interim center Minimum Data Set (MDS), NACC has successfully refined and expanded the overall database, reduced missing data, increased data validity, expanded neuropathological data, added Center-wide data surveys, and increased accessibility to the data through the use of web-based data access and entry. The capabilities provided for use of combined ADC data have not been experienced by the ADCs prior to the establishment of NACC. With over 60,000 subjects, this is currently the largest Alzheimer's and related disorders database ever assembled in the U.S. NACC was additionally charged with increasing collaboration between the ADCs, not only through the use of the MDS but also through the promotion of investigator-initiated collaborative projects and the provision of statistical, methodological and database management consulting to the ADCs and for the collaborative projects. In the next grant cycle, NACC will continue to expand on these efforts. The Uniform Data Set (UDS) has now been mandated for use in all ADCs by NIA. NACC will build a database structure to implement the UDS, collect the data and integrate it seamlessly with the existing data. NACC will develop a means of capturing referral source and selection method data for all new UDS enrollees. These data will help describe and increase the external validity of analyses which use the database and will form the basis for ADCs to select the most comparable controls for their cases. NACC wilt continue its successful collaborative project program and will also encourage small secondary data analysis studies from junior investigators. NACC will continue design and analysis consulting, and expand its efforts to increase communication and collaboration through the NACC web site. NACC will also conduct its own data analyses and develop methodological research relevant to the needs of the ADCs and research in general. Finally, NACC will continue its administrative coordinating activities to facilitate meetings of the ADC Directors and Core Leaders.